A suite of engineered mice for interrogating psychedelic drug actions

Introduction

Serotonin (5-HT) modulates mood, perception, cognition, and a broad range of physiological functions through a family of 14 receptor subtypes, nearly all of which are G protein-coupled receptors. Of these, the 5-HT2A receptor (HTR2A) has attracted particular attention as the primary molecular target for classical psychedelic drugs — including LSD, psilocybin, DMT, and mescaline — as well as a high-affinity binding site for most atypical antipsychotics and many antidepressants. Despite decades of research, investigation of HTR2A function in psychedelic drug action has been hindered by the lack of validated genetic tools, with available reporter mouse lines showing inconsistent or inaccurate expression patterns relative to established autoradiographic and in situ hybridisation data. The present study aimed to develop and validate a suite of genetically engineered mice — collectively termed AMIS — to provide open-source platforms for interrogating the species specificity, cellular signalling, neural circuitry, and behavioural actions of psychedelic drugs. Using CRISPR/Cas9 genome editing, the researchers generated novel HTR2A-EGFP knock-in and HTR2A-EGFP-CreERT2 lines that faithfully recapitulate the endogenous expression and function of the receptor, enabling cell-type-specific circuit mapping and in vivo pharmacological interrogation with unprecedented precision.